Is salivary estriol detectable in very early pregnancy?

OBJECTIVE: Estriol (E3) is produced by the placenta and is important for early pregnancy maintenance. In blood, E3 can be detected from the 8th week of pregnancy. Under the influence of the hypothalamic-pituitary-adrenal (HPA) axis hormone ACTH, E3 levels increase sharply after the 10th week. Although E3 can be reliably analyzed in saliva, till now information about the concentrations during the first trimester is missing. The aim of this study was to verify whether the sensitivity of a newly developed enzyme immunoassay is sufficient for the determination of salivary E3 (sE3) in very early pregnancy. METHODS: Saliva samples were collected at home, once weekly in 25 healthy pregnant women from the 6th week of gestation to the end of the first trimester. RESULTS: sE3 was detectable from the beginning of the 6th pregnancy week (M = 3.17 pg/ml, SD = 2.13). A steep significant increase between the 7th and the 8th week (p = 0.029) and again between the 10th and the 11th week (p = 0.001) was apparent. CONCLUSION: Low concentrations of sE3 can be measured during very early pregnancy and may serve as a promising, easily assessable marker for future research on the mechanisms of healthy pregnancy.